1. Field of the Invention
The present invention relates generally to methods and apparatus for shielding branched wiring harnesses and their protective conduits so as to prevent noise caused by the penetration of interfering electromagnetic fields.
2. Background Discussion
Contemporary spacecraft, aircraft, water craft, and complex land vehicles use control, communication, and navigation systems that are critical to safety and efficient operation. These systems are largely, if not entirely, electronic, and they are typically connected and interconnected using multiple bundles of wires. This fact presents design challenges in routing and shielding the wires, as well as any conduits through which the wires are routed, as the systems identified can be quite sensitive. In many applications literally thousands of wires are routed so as to be in close proximity to other wires, wire conduits, and electronic systems. Accordingly, the wires and the signals on the wires are vulnerable to ambient EMI and RFI from neighboring wires and systems.
Because of this long appreciated problem with interference, shielding has reached a considerably high level of maturity. At present, circuits that must be protected from interference are typically provided with metallic braided shielding comprising tin- or nickel-plated copper strands. Additional insulation from interference can be provided by incorporating metallic foils in the wire bundle and/or by wrapping wire and metallic fabric around the wire bundle cover or the conduit through which the bundle is routed.
Generally, wire circuits are segregated and bundled together according to their sensitivity to EMI and RFI, and circuit noise in any given bundle is reduced by wrapping the entire bundle in a braided shield and/or routing the bundle through a conduit. However, the shield on the wire bundle or on the conduit must have electrical continuity and a low resistance connection to ground. Accordingly, at any point at which a main conduit for a main cable bundle must branch into smaller conduits for smaller wire bundles, the conventional practice is to interrupt the braided shield and to insert a metal fitting to which the individual shields of the main and branch conduits are each attached, thereby maintaining shield continuity. The ground connection is then made to the metal branch fitting.
However, the connections between shielding for the conduit branches and the main conduit at the branching point is particularly vulnerable to separation, and thus to reduced effectiveness in shielding and a potential break in the ground connection. However, because the applications call for lightweight components, it is desirable to have a robust but lightweight junction in the shielding between a main conduit and conduit branches.